The dawn of 2016 brought with it the arrival of a new medication option for patients struggling to control symptoms of ankylosing spondylitis (AS) and psoriatic arthritis (PsA). The medication, secukinumab (Cosentyx), was already approved by the U.S. Food and Drug Administration (FDA) for the treatment of psoriasis, a condition that causes the skin to form scaly patches that are often itchy and painful. Now FDA has given doctors the go-ahead to prescribe secukinumab to people with AS and PsA, two forms of inflammatory arthritis that can be a challenge to manage.

Secukinumab, an injectible biologic, belongs to an emerging subgroup of drugs that target a molecule interleukin-17A (IL-17A). Produced by the immune system, IL-17A helps protect the body against infections. IL-17A works by promoting inflammation to destroy bacteria and other germs that can cause illness. But if the body produces too much of this molecule, it can trigger problems, including pain and damage to joints and other tissues. Secukinumab is a type of drug known as monoclonal antibody, which is a protein capable of binding to other substances. Secukinumab latches on to IL-17A and prevents it from locking into cell receptors, disabling its ability to cause inflammation.

IL-17A levels tend to be elevated in people with AS, a condition that causes severe pain and stiffness in the joints, primarily those in the spine. That led scientists to suspect that secukinumab might offer a new approach to treating this often-debilitating disease. Some patients with AS get relief from nonsteroidal anti-inflammatory drugs (NSAIDs) and a kind of biologic known as a TNF inhibitor. “But not every patient responds to existing therapies,” says rheumatologist Atul Deodhar, MD, of the Oregon Health and Science University, in Portland. “Effective new treatment options are needed.”

Meanwhile, IL-17A has also been linked to PsA, another autoimmune form of arthritis, which occurs in up to 30 percent of people who have psoriasis.

“Secukinumab is an important new therapy,” says rheumatologist Susan Goodman of the Hospital for Special Surgery, in New York City, who was not involved in these clinical trials. Not only does the availability of secukinumab offer a much-needed new treatment alternative for AS and PsA, says Dr. Goodman, but these studies have helped to confirm that the IL-17 family of immune system molecules is a valid target for developing future treatments for people who have these conditions.